Circatrigintan rectal temperature and endocrine rhythms of clinically healthy, menstrually cycling women

Rectal temperatures were measured automatically every 10 min for part or most of two menstrual cycles in ten clinically healthy young women, 20-30 years of age, with a wearable instrument, the Polychronor. Occasional malfunction of the instrumentation resulted in corresponding gaps in the series. Data were examined by chronograms, plexograms, and chronobiologic serial sections computed with the fit of a 24-hr period, population-mean cosinor, and linear-nonlinear least-squares analyses. Single cosinor-derived circadian parameters were next fitted with a cosine curve of a period equal to the number of days of the corresponding intermenstruum. Second-order infradian inferential statistics were calculated next; the first day of menstruation was used as acrophase reference. A population-mean cosinor at the intermenstrual period yields a temperature acrophase of -279 degrees, with the 95% confidence interval extending from -254 degrees to -312 degrees. Since the intermenstruum differs in different subjects and/or in different menstrual cycles of a given woman, this acrophase corresponds to different time intervals from the first day of menstruation in different cases. This acrophase thus indicates the relative timing within the menstrual cycle of overall high rectal temperatures. On four subjects in four stages of their menstrual cycle, plasma was also obtained at 2-hr intervals around the clock. Ten hormones were determined. The sparse endocrine sampling along the menstrual cycle notwithstanding, a circatrigintan rhythm in all hormones investigated was demonstrated for a woman 26 years of age. At the period corresponding to the intermenstrual interval, the acrophases for T3, cortisol, FSH, testosterone, DHEA-S, T4, and LH occurred before the circatrigintan rectal temperature acrophase, whereas the acrophases for prolactin, estradiol, and progesterone occurred near or shortly after the rectal temperature acrophase. Whereas earlier circatrigintan mapping of adult women had been summarized on a group basis, this study allows individualized circatrigintan rhythm assessment. Circatrigintan, like circadian and circannual, acrophase and amplitude relations do not necessarily imply causal relations, yet they are an indispensable quantitative reference standard for the study of basic mechanisms and for diagnosis and intervention, including endeavors in planned parenthood that might take into account the organism's dynamics with multiple frequencies.